Assuming word_count is a map from string to size_t and word is a string, explain the following loop

while (cin >> word)
      ++word_count.insert({word, 0}).first->second

The code just does the same thing as `++word_count[word];`. If the `word` is in `map`, then increase the count of that word by 1, else insert that word into `map`, set the count to 0, and increase the count by 1.